invoice him for the true and total cost of the usage, not a penny less . . . While he's sincere he knowingly use your photo without permission, he also know's that using images comes with a cost. I would not gouge him, i would charge full rate. The reason youre asking is because youre not in business yet. I can not understand why so many photographers diminish the value of their product and their worth . . . I'm not malicious and i more often than not negotiate and give deference to mistakes, we all make them, but in this case, you charge full price or youre only sending the message that photographers dont value their work . . .